Reddit reviews SHIMANO Tourney TX55 6/7 Speed Rear Derailleur

This is a direct replacement.

Here is how to replace it

In broad strokes there are five things you need to consider, in order of importance:

1 - How does the derailleur mount to your frame? If you have a hanger with a threaded hole below the dropout you use the "normal" modern style like so

Otherwise if your dropouts (mostly older frames) don't have a hanger you need to use one like this or get an adapter.

2 - (Again broad strokes, there are exceptions) you need to consider the brand. Don't mix Shimano with SRAM.

3 - You need a derailleur for the number of cogs in your rear cassette / freewheel. A 10-speed mountain rear derailleur won't work with 9-speed mountain shifters, for example. There are, again, exceptions but that gets very complicated very quickly.

4 - You need a rear derailleur capable of taking up all the chain slack your gears will create. The rear derailleur not only shifts the rear, it also uses that long dangling cage with two pulleys to tension the chain. The amount of chain used when in the big chainring up front is a lot more than the amount of chain used when in the small. The rear derailleur doesn't shift those front chainrings, but it does take up the slack. You need a rear derailleur which can take up all the slack your chosen drivetrain can generate. (BigChainring-SmallChainring)+(BigCog-SmallCog)=How much slack a drivetrain generates. The longer the "cage" the more chain slack a rear derailleur can tension, but the worse it shifts (in theory) and the more likely it is to get hit by trail obstacles (because it hangs lower). That's why most people run the smallest cage they can. Cages come in three general length categories: Short, medium, and long. MTB cages are almost always medium or long, and road cages are almost always short or medium.

5 - Clutch or not. Clutch derailleurs are (in theory) harder to shift but they don't bounce around as much off road, preventing the chain from bouncing as much on rough terrain, decreasing the chance of the chain popping off the front chainring.


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As far as "what's better than what": Longish article on Shimano and SRAM's heirarchies

Do you really have the derailleur hanger? You should post the pic of broken one so that we can make sure.

If you do have the derailleur hanger, I think you can use something like this. Shimano Tourney.

https://www.amazon.com/Shimano-Tourney-TX55-Speed-Derailleur/dp/B003ZM9RDQ/ref=pd_sim_468_10?_encoding=UTF8&pd_rd_i=B003ZM9RDQ&pd_rd_r=X7ESM3A6V3YXM80YCV7T&pd_rd_w=k6Gma&pd_rd_wg=hsYVC&psc=1&refRID=X7ESM3A6V3YXM80YCV7T

There are a few details that matter for your derailleur.

• If the current one is a SRAM, the new one needs to be a SRAM.
  
  
• If the current derailleur has an integrated claw-type hanger (like this one does, as opposed to this one) then you want to get the same thing.
  
  If neither of the above apply to you, then you can buy just about anything else out there.
  
  If you don't have indexed shifting, or if you do, and you have less than 8 gears in the back, then you can get away with really cheap cables. WalMart and Amazon sell a Bell-branded kit with everything you need for $6.
  
  Take note of the cable routing as you take the old parts off, and use the old housing sections as a guide to cut the new ones (even if you need to make some changes). Also, read this first. You don't really need special tools, but you will need to do some clean-up work on the cut housing ends with a file.